1. Field of the Invention
The present invention relates to a platen cover for a copier or scanner. More in particular, the invention relates to a non-imageable platen cover that includes on a surface thereof a fluorescent coating.
2. Discussion of Related Art
Copiers, scanners and like devices (hereinafter referred to as imaging devices) make duplicate images from original document images by first exposing the original document image with a light source or other optical system at an imaging station. The original document is placed on a glass platen at the imaging or exposure station of the device for the exposure step. The device is provided with a platen cover that is preferably brought over the surface of the original document and glass platen at least during the exposure step.
The platen cover for a conventional document copier, scanner, etc., device is constructed of a high diffuse reflectance white surface. This high diffuse reflectance white surface is illuminated by the light source when the original document lying on the glass platen surface is scanned. By constructing the platen cover of the document scanner with a high diffuse reflectance white surface, the background of the white document and the surrounding platen cover surface presents a similar, high reflectance to the optical system and photosensor or photoreceptor below the glass platen.
The high diffuse reflectance white surface enables the conventional document scanner or copier to reduce or eliminate dark borders around the copy document, black circles where punch holes exist in the original document, and dark borders around multiple images such as multiple receipts on a single scan. Moreover, the high diffuse reflectance white surface enables the conventional document scanner to improve the contrast of the document's image by reflecting light which is transmitted through the input document.
However, use of a dark platen cover is also desirable in many instances. For example, a dark platen cover can reduce the show-through of the image on a backside of an original paper document, which is particularly important when thin paper originals are being scanned or copied. Unfortunately, if the original document has uneven borders or punched holes, use of a dark platen cover renders a duplicate image that has unsightly black borders and/or black dots/holes within the duplicate image.
One solution to the use of dark platen covers might be to eliminate unsightly borders and hole punching through image control programs that detect these portions of an original and adjust the duplicate image to eliminate these portions. However, these types of control programs are expensive and time consuming to operate.
U.S. Pat. No. 5,790,211, incorporated herein by reference in its entirety, proposes another solution. This patent describes a system and method that digitally scans a document and uses a platen cover that can switch between a high reflectance mode and a low reflectance mode. Initially, the platen cover provides a low reflectance background around the document and the scanner scans the low reflectance background and document to determine an edge of the document or to retrieve other image characteristics of the document. Subsequently, the platen cover changes so as to provide a high reflectance background around the document. The scanner then scans the high reflectance background and the document and produces digital image data relating to an image on the document. The platen cover is enabled to change to the high reflectance mode through control of a liquid crystal light located on a surface of the platen cover backing member that is adjacent to the glass platen.
What is still desired is an improved platen cover that is low in cost to manufacture, operates simply, and overcomes the deficiencies of the platen covers discussed above.
U.S. Pat. No. 5,754,921, incorporated herein by reference in its entirety, describes an original density detecting apparatus that includes a projector-receiver including a light projector and a light receiver, and a reflecting member including a fluorescent reflecting plate, a surface of which on the projector-receiver side has a coating of a fluorescent dye. An imaging apparatus includes an illuminating device for illuminating an original, an image reader for forming an image of the original on a photosensitive medium, and the original density detecting apparatus as described above. This patent does not teach or suggest a platen cover that includes a fluorescent coating on a surface thereof, the fluorescent surface in this patent being used only in conjunction with a density detection apparatus which is removed from the area where the original document is illuminated with the illuminating device. The density detection apparatus does not include a platen or platen cover, and is not located at the exposure station (light source 115) of the device.